1. Field
The present disclosure relates generally to fiber optic devices and systems and in particular to a method and apparatus for detecting liquids. Still more particularly, the present disclosure relates to a method and apparatus for detecting fuel in a fuel tank.
2. Background
The amount of fuel present in an aircraft fuel tank is important for a pilot to know. The amount of fuel present can be used to verify fuel consumption of a flight. Measuring fuel levels in an aircraft fuel tank may be made using a fuel measurement system, such as a fuel gage. These systems include a sender unit and an indicator. The sending unit may be for example, a float connected to a variable resistor. The indicator may be an analog readout or a digital display of the amount of fuel present in the fuel tank.
In an aircraft, a capacitive probe is as another example of a sender unit. Multiple probes may be mounted within the fuel tank in low voltage capacitors are present. The fuel may go between the capacitors in the probes. At different fuel levels, different capacitances are present. The capacitance, in these types of systems, is proportionate to the height of the fuel in the tank. By receiving the capacitance values, the amount of fuel present in the fuel tank may be determined. This component, however, requires these components and wiring to be placed into the fuel tank.
Although they are reliable, failures do occasionally occur in a probe, requiring the aircraft to be taken out of service for maintenance. The replacement of one or more probes may take several days. Consequently, the aircraft is out of commission for this type of maintenance. Therefore, it would be advantageous to have a method and apparatus for detecting fuel that reduces the need for maintenance.